Tyrosinase Essay

Enzymes are biological macromolecule that acts as catalysts and increase the rate of a chemical reaction. Without enzymes, life, as we know about it, would not exist. Enzymes function by deceasing the activation energy and stabilizing the transition state of a chemical reaction without altering the thermodynamic of reaction (#1 Boyer). At the molecular level, enzymes catalyze these reactions by binding to the substrate or reactants to form an enzyme-substrate complex. The reaction takes place while the substrate is bound to the enzyme and converting the substrate to the new product. The new product is then released from the enzyme substrate complex, and the enzyme is then free to bind with more substrate. E+S → ES → E+P (#1 Boyer). Based on

The system involved in this lab was L-dopa as a substrate, enzyme was Tyrosinase, and the product was Dopachrome. Tyrosinase is commonly known as polyphenol oxidase, an enzyme that present in plant and animal cell (#1 Boyer). In plant cell, the biological function if Tyrosinase is unknown, but its presence is readily apparent. Tyrosinase is also involved in the browning of fruits, tubers, and fungi that have been damaged. In mammalian cell, Tyrosinase is involved in melanin synthesis, which gives skin its color. It will act on the substrate L-dihydroxyphenylalanine (L-Dopa) and convert to Dopachrome, which is the product that has color, and it can measure at 475nm using the Spectrophotometer. This work based on the Beer-Lambert’s Law (A=εlc), A stands for Absorbance, ε is extinction coefficient or the molar absorptivity (M-1 cm-1), and l is the path length (distance) that light passes through the sample (cm), c is a concentration of solution (M) (#3 Ninfa, Ballou, Benore). Beer- Lambert Law predicts a linear relationship between absorbance and the concentration of a chemical species being analyzed. It states that the absorbance (A) of a sample solution is directly proportional to the concentration (c) of the absorbing colored

Cinnamic is an organic compound that slightly soluble in water, and freely soluble in many organic solvents. Cinnamic acid is used in flavors and certain pharmaceuticals. According to vernier.com, the inhibitor type of Cinnamic Acid was non-competitive inhibitor (#4 vernier.com). In order to observed and analyze the effects of changing mushroom Tyrosinase and L-dopa concentrations on reaction rates, and to figure out what type inhibitor of Cinnamic acid, we was used the data to construct the Michaelis-Menten and Lineweaver- Burk plots. The Michaelis-Menten is the common known models of enzyme kinetic. The model demonstrates how the reaction rate relates to the concentration of substrate and enzyme. The rate equation of these enzymes is characterized by a sigmoidal curve. Using this graph we can determine the Km and Vmax. The Vmax is the maximum velocity achieved at the maximum substrate concentration. Km represents the Michaelis-Menten constant. It is the substrate concentration at which the reaction velocity is ½ Vmax. At this concentration, half of the enzyme molecule in solution is bounded to the substrate (#5 chemwiki.ucdavis.edu). The Lineweaver-Burk plot is the graph obtained by taking the reciprocal of the Michaelis-Menten Kinetics equation, which give you a linear line (#5 chemwiki.ucdavis.edu). The linear data is easier to read and